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28 Cards in this Set
- Front
- Back
Which nucleotide bases make up the purines and which are the pyrimidines? Which are used in DNA and which in RNA?
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Purines: Adenine, Guanine (Pure As Gold)
Pyrimidines: Cytosine, Uracil, Thymine (CUT the PYe) DNA: A, G, C, T RNA, A, G C, U |
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Nucleotide A pairs with ___ and C pairs with ___ in a DNA strand.
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A with T
C with G |
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Gene transcription begins in the ____ of the cell with the creation of what?
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Nucleus; mRNA
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What is the enzyme that pries the 2 strands of DNA apart and transcribes one strand into mRNA?
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RNA polymerase
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RNA polymerase attaches and initiates transcription at the ____ of the DNA strand.
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Promoter
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What regulates whether a section of DNA gets transcribed into mRNA?
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Transcription factors
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In DNA replication, the nucleotides are added:
A: 5' to 3' B: 3' to 5' C: Both |
5' to 3'
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What organ(s) does most of the synthesis of the purines and pyrimidines?
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Mainly liver, but also brain. The liver creates nucleosides that enter the bloodstream and travel to other tissues to get converted into nucleotides.
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What is the hexose monophosphate shunt? What is the key enzyme involved? What is the other name for pathway?
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It is an alternate pathway for glucose 6-phosphate to enter to create ribose 5-phosphate which can then be used for purine and pyrimidine nucleotides.
The main enzyme is Glucose-6-P Dehydrogenase; it's a rate-limiting step and the products are CO2, 2 NADPH, and Ribulose 5-P. Pentose Phosphate Pathway |
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From Ribose 5-phosphate, what is the pathway to manufacture A, T, C, G and U?
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Ribose 5-P conerts to PRPP. For purine synthesis (A, G), PRPP gets converted to IMP and then to AMP and GMP. This process requires glycine, aspartate, glutamine and THF (TetraHydroFolate).
For pyrimidine synthesis, the PRPP is joined with orotic acid to form UMP. The orotic acid is formed from carbomoyl phosphate and aspartate. Note that carbomoyl phosphate is also used in the urea cycle. |
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What's the difference between a nucleoside and nucleotide?
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Nucleoside = base + ribose
Nucleotide = base + ribose + phosphate; they're linked together by phosphodiester bonds |
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What are purines catabolized to? What are pyrimidines catabolized to?
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Purine degradation generates uric acid.
Pyrimidines degrade into CO2 and urea. |
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What is the enzyme that is used in the degradation of the purines?
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Xanthine oxidase.
Guanine is degraded directly to xanthine. Adenine is degraded to hypoxanthine and then xanthine. Xanthine oxidase is used in both the oxidation process of hypoxanthine to xanthine and the xanthine to uric acid. |
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Where does translation occur?
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In the cytoplasm
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Where does transcription occur?
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In the nucleus
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What does it mean when we say our genetic code is unambiguous and redundant?
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Each codon specifies only 1 amino acid and more than 1 codon may code for the same amino acid.
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What is the start codon?
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AUG
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What are the stop codons?
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UGA - U Go Away
UAA - U Are Away UAG - U Are Gone |
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What 3 things occur to the mRNA before it's transported out of the nucleus?
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1) 5' cap
2) Polyadenylation on 3' end (approx 200 A's) 3) Splicing out of introns (remember: EXons EXit and are EXpressed) |
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What is attached to defective proteins to tag them for breakdown?
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Ubiquitin
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What is used in the cytoplasm to create a protein?
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Ribosome (2 subunits come together: 40S + 60S for eukaryotes)
mRNA - This is the strand that gets translated tRNA - brings in the appropriate amino acid that's bound to its 3' end rRNA - transfers growing polypeptide to amino acid in "A" site of ribosome |
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What is a point mutation in DNA?
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Single base pair alteration in DNA leading to a single amino acid change in a protein.
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What type of genetic mutation is Sickle Cell Anemia?
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Point mutation
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What type of genetic mutation is fragile X syndrome? What type is Huntingtons?
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They are both trinucleotide repeats. Fragile X syndrome is CGG repeats in X chromosome leading to mental retardation.
Huntington's is CAG repeats in chromosome 4. |
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What are the odds that an affected person with an autosomal dominant disorder will have a child with the disorder?
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50%
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What are the odds that an affected person with an autosomal recessive disorder will have a child with the disorder?
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25%
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X-linked dominant traits would show up how?
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If the mother had it, there's a 50% chance a son or daughter would get it. If the father had it, the sons would not get it, the daughters would all get it.
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What type of genetic inheritance is Hemophilia A and Duchenne's muscular dystrophy?
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X-linked recessive
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